No specific noise reduction strategies to restrict noise exposure less than 45 dB combined with either continuous bright light or continuous near darkness or unstructured combination of the two during the hospitalization.

Reduced noise exposure (sound levels <45 dB) and cycled light (approximately 12 hours of light on and 12 hours of light off).

Reduced noise exposure (sound levels <45 dB) and cycled light (approximately 12 hours of light on and 12 hours of light off).

FVEP is recorded from each eye individually after they fall asleep. Three silver-sliver chloride electrodes are placed according to 10-20 International system with active electrode at Oz (1-2 cm above inion), reference electrode at Fz and ground electrode at Cz. Scalp-electrode impedance is usually below 5kΩ but always below 10kΩ. Flash stimulus (2 Hz.) is given by light emitting diode goggles simulator at a distance of 2 cm to one eye at a time. 100 responses are averaged for each eye automatically in the Nicolet Viking Quest visual electrophysiological device at 1s total sweep time. Band pass filters are set at 0.1-75 Hz. The reproducibility of the responses is ensured by repeating the test two or more times. Responses with excessive artifacts are automatically rejected. The parameters of P1, N1, P2, N2, P3, and N3 of the FVEP are stored and subsequently assessed by ophthalmologist blinded to the infant's clinical course.

Neurodevelopment outcome is measured with the Bayley Scales of Infant Development, Second Edition (BSID-III) at corrected gestational age of 18 month, assessed by the physician from department of child health care who was blinded with respect to the subjects. Mental and motor scores were calculated by the BSID-III Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI). The subject's neurodevelopmental outcome was classified as delayed if either score was less than 70.

up to 3 months

up to 3 months